The high density storage of hydrogen as a fuel for controlled release and combustion with oxygen to provide energy is of current interest. Conventional high pressure storage in the compressed gas or liquidized state is undesirable because of the high pressure involved, the bulk weight of the containers, and inherent danger in pressurized systems. Other techniques for hydrogen storage have included the utilization of material having the chemical binding capability for reversibly storing, and therefore releasing, hydrogen gas at relatively low temperatures and pressures. A number of materials have evolved for this purpose including certain rare earth-transition materials and in particular samarium-cobalt, SmCo.sub.5 and lanthanum-nickel, LaNi.sub.5. One of the serious limitations in the previous use of samarium-cobalt and similar materials is their structural instability over repeated absorption/desorption cycles of hydrogen storage and release.
Samarium-cobalt and similar rare earth-transition metal materials have a crystalline atomic structure characterized by a systematized arrangement of atoms within a lattice structure which differs from material type to material type. Recent investigations point to the existence of crystal structure strains resulting from repeated absorption and desorption of hydrogen gas as being at least partially responsible for the fracturing of the hydrogen storage material under such repeated cycling.
The results of such fracturing impair the use of the material in a hydrogen storage cell. In the case where such material is used as a plurality of exposed sheet surfaces in a labyrinth of passages through which hydrogen is pumped, the fracturing would clearly destroy the physical and mechanical integrity of the cell. In other cases in which a fluidized bed of particulate material is employed, the particle size is important to proper aeration of the fluidized bed whereas repeated fracturing results in particles of such small size that they pack in dense clumps which can not be effectively fluidized thereby greatly reducing the effective storage capacity of the cell.